Pixel and organic light emitting display device having the pixel

ABSTRACT

A pixel includes a plurality of transistors, a storage capacitor, and an organic light emitting diode. A first transistor controls the amount of current from a first driving power source to the organic light emitting diode based on a data voltage. A second transistor is connected to a data line and is turned on based on a scan signal. A third transistor coupled to the first transistor and is turned on based on the scan signal. A first stabilizing transistor is coupled to the third transistor or between the first and third transistors and is turned off when the third transistor is turned off.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This is a divisional application based on pending U.S. patentapplication Ser. No. 15/811,922, filed on Nov. 14, 2017, the disclosureof which is incorporated herein by reference in its entirety. U.S.patent application Ser. No. 15/811,922 claims priority benefit of KoreanPatent Application No. 10-2016-0162995, filed on Dec. 1, 2016 in theKorean Intellectual Property Office, and entitled, “Pixel and OrganicLight Emitting Display Device Having the Pixel,” the disclosure of whichis incorporated by reference herein in its entirety for all purposes.

BACKGROUND 1. Field

One or more embodiments described herein relate to organic lightemitting display device and pixel in such a device.

2. Description of the Related Art

A variety of displays have been developed. Examples include liquidcrystal displays and organic light emitting displays. An organic lightemitting display generates images based on light emitted from pixelsthat include organic light emitting diodes. Organic light emittingdisplays have high response speed and low power consumption.

In an organic light emitting display, data lines and scan lines carrysignals for driving the pixels. The pixels have driving transistors thatcontrol the amounts of current flowing through corresponding organiclight emitting diodes. Specifically, each driving transistor controlsthe amount of current flowing from a first driving power source to asecond driving power source, via the organic light emitting diode, basedon a data signal. Light is emitted with a predetermined luminancecorresponding to the amount of current from the driving transistor.

Various methods have been proposed to control luminance in an organiclight-emitting display. One method involves setting the second drivingpower source to a low voltage. Another method involves reducing powerconsumption by driving the display at a low frequency. However, thesemethods have drawbacks, e.g., predetermined leakage current may begenerated from the gate electrodes of the pixel driving transistors. Asa result, voltages of the data signals are not maintained during oneframe period, which, in turn, adversely affects luminance.

SUMMARY

In accordance with one or more embodiments, a pixel includes an organiclight emitting diode; a first transistor coupled between a first drivingpower source coupled to a first node and an anode electrode of theorganic light emitting diode, the first transistor to control the amountof current from the first driving power source to the organic lightemitting diode based on a voltage of a second node; a second transistorcoupled between a data line and the first node, the second transistor tobe turned on when a first scan signal is supplied to an ith (i is anatural number) first scan line; a third transistor coupled between asecond electrode of the first transistor and the second node, the thirdtransistor to be turned on when the first scan signal is supplied; astorage capacitor coupled between the first driving power source and thesecond node; and a first stabilizing transistor coupled between thethird transistor and the second node or between the second electrode ofthe first transistor and the third transistor, the first stabilizingtransistor to be set to a turn-off state during a portion of a period inwhich the third transistor is turned off. The first transistor, secondtransistor, and third transistor may be P-type poly-siliconsemiconductor transistors. The first stabilizing transistor may be anN-type oxide semiconductor transistor.

A gate electrode of the first stabilizing transistor may be coupled to acontrol power source, the control power source may be set to a gate-onvoltage during a period in which the pixel is driven at a first drivingfrequency and to a gate-off voltage during a portion of a period inwhich the pixel is driven at a second driving frequency lower than thefirst driving frequency. When the pixel is driven at the second drivingfrequency, the control power source may be set to the gate-off voltageafter a voltage of a data signal is stored in the storage capacitor.

The pixel may include a sixth transistor coupled between the first nodeand the first driving power source, the sixth transistor to be turnedoff when a light emitting control signal is supplied to an ith lightemitting control line and turned on at a time when the light emittingcontrol signal is not supplied to the ith light emitting control line;and a seventh transistor coupled between the second electrode of thefirst transistor and the anode electrode of the organic light emittingdiode, the seventh transistor to be turned on or turned offsimultaneously with the sixth transistor, wherein the light emittingcontrol signal supplied to the ith light emitting control line is set toa wider width than the first scan signal and is supplied to overlap thefirst scan signal. The gate electrode of the first stabilizingtransistor may be coupled to the ith light emitting control line.

The pixel may include a fourth transistor coupled between the secondnode and a first power source, the fourth transistor to be turned onwhen a second scan signal is supplied to an ith second scan line; and asecond stabilizing transistor coupled between the second node and thefourth transistor or between the fourth transistor and the first powersource, the second stabilizing transistor to be set to the turn-offstate during a portion of a period in which the fourth transistor isturned off. The first power source may be set to a lower voltage thanthe data signal supplied to the data line. The second stabilizingtransistor may be an N-type oxide semiconductor transistor.

A gate electrode of the second stabilizing transistor may be coupled toa control power source, and the control power source may be set to agate-on voltage during a period in which the pixel is driven at a firstdriving frequency and set to a gate-off voltage during a portion of aperiod in which the pixel is driven at a second driving frequency lowerthan the first driving frequency. When the pixel is driven at the seconddriving frequency, the control power source may be set to the gate-offvoltage after a voltage of a data signal is stored in the storagecapacitor.

The pixel may include a sixth transistor coupled between the first nodeand the first driving power source, the sixth transistor to be turnedoff when a light emitting control signal is supplied to an ith lightemitting control line and turned on otherwise; and a seventh transistorcoupled between the second electrode of the first transistor and theanode electrode of the organic light emitting diode, the seventhtransistor to be turned on or turned off simultaneously with the sixthtransistor, wherein the light emitting control signal supplied to theith light emitting control line is set to a wider width than the firstscan signal and is supplied to overlap the first scan signal. The gateelectrode of the second stabilizing transistor may be coupled to the ithlight emitting control line. The ith second scan line may be set as an(i−1)th first scan line.

The pixel may include a fifth transistor coupled between the anodeelectrode of the organic light emitting diode and a first power source,the fifth transistor to be turned on when a third scan signal issupplied to an ith third scan line; and a third stabilizing transistorcoupled between the anode electrode of the organic light emitting diodeand the fifth transistor or between the fifth transistor and the firstpower source, the third stabilizing transistor to be set to a turn-offstate during a portion of a period in which the fifth transistor isturned off. The third stabilizing transistor may be an N-type oxidesemiconductor transistor.

A gate electrode of the third stabilizing transistor may be coupled to acontrol power source, the control power source may be set to a gate-onvoltage during a period in which the pixel is driven at a first drivingfrequency and to a gate-off voltage during a portion of a period inwhich the pixel is driven at a second driving frequency lower than thefirst driving frequency. When the pixel is driven at the second drivingfrequency, the control power source may be set to the gate-off voltageafter a voltage of a data signal is stored in the storage capacitor.

The pixel may include a sixth transistor coupled between the first nodeand the first driving power source, the sixth transistor to be turnedoff when a light emitting control signal is supplied to an ith lightemitting control line and turned on otherwise; and a seventh transistorcoupled between the second electrode of the first transistor and theanode electrode of the organic light emitting diode, the seventhtransistor to be turned on or turned off simultaneously with the sixthtransistor, wherein the light emitting control signal supplied to theith light emitting control line is set to a wider width than the firstscan signal and is supplied to overlap the first scan signal. The gateelectrode of the third stabilizing transistor may be coupled to the ithlight emitting control line. The ith third scan line may be set as theith first scan line.

In accordance with one or more other embodiments, a pixel includes anorganic light emitting diode; a first transistor to control an amount ofcurrent flowing from a first driving power source to a second drivingpower source, via the organic light emitting diode, based on a voltageof a first node; a second transistor coupled between a data line and thefirst node, the second transistor to be turned on when a scan signal issupplied to a scan line; a storage capacitor coupled between the firstnode and a second electrode of the first transistor; and a stabilizingtransistor coupled between the data line and the second transistor orbetween the second transistor and the first node, wherein the firsttransistor and the second transistor are N-type poly-siliconsemiconductor transistors and the stabilizing transistor is an N-typeoxide semiconductor transistor.

A gate electrode of the stabilizing transistor may be coupled to acontrol power source, the control power source may be set to a gate-onvoltage during a period in which the pixel is driven at a first drivingfrequency and set to a gate-off voltage during a portion of a period inwhich the pixel is driven at a second driving frequency lower than thefirst driving frequency.

When the pixel is driven at the second driving frequency, the controlpower source may be set to the gate-off voltage after a voltage of adata signal is stored in the storage capacitor. The gate electrode ofthe stabilizing transistor may be coupled to the scan line. The pixelmay include a third transistor coupled between the first driving powersource and a first electrode of the first transistor, the thirdtransistor having a turn-on period not overlapping the secondtransistor.

In accordance with one or more other embodiments, a pixel includes anorganic light emitting diode; a first transistor to control an amount ofcurrent flowing from a first driving power source to a second drivingpower source, via the organic light emitting diode, based on a voltageof a first node; a second transistor coupled between a data line and asecond node, the second transistor to be turned on when a scan signal issupplied to a scan line; a third transistor coupled between the secondnode and a second electrode of the first transistor, the thirdtransistor to be turned off when a light emitting control signal issupplied to an (i−1)th light emitting control line; a fourth transistorcoupled between the first node and a first electrode of the firsttransistor, the fourth transistor to be turned on when the scan signalis supplied; a storage capacitor coupled between the first node and thesecond node; and a first stabilizing transistor coupled between thefirst node and the fourth transistor or between the fourth transistorand the first electrode of the first transistor, wherein the first tofourth transistors are N-type poly-silicon semiconductor transistors andthe first stabilizing transistor is an N-type oxide semiconductortransistor.

A gate electrode of the first stabilizing transistor may be coupled to acontrol power source, and the control power source may be set to agate-on voltage during a period in which the pixel is driven at a firstdriving frequency, and set to a gate-off voltage during a portion of aperiod in which the pixel is driven at a second driving frequency lowerthan the first driving frequency.

When the pixel is driven at the second driving frequency, the controlpower source may be set to the gate-off voltage after a voltage of thedata signal is stored in the storage capacitor. The gate electrode ofthe first stabilizing transistor may be coupled to the scan line. Thepixel may include a second stabilizing transistor coupled between thedata line and the second transistor or between the second transistor andthe second node. The second stabilizing transistor may be an N-typeoxide semiconductor transistor.

A gate electrode of the second stabilizing transistor is coupled to acontrol power source, and the control power source is set to a gate-onvoltage during a period in which the pixel is driven at a first drivingfrequency and set to a gate-off voltage during a portion of a period inwhich the pixel is driven at a second driving frequency lower than thefirst driving frequency. When the pixel is driven at the second drivingfrequency, the control power source may be set to the gate-off voltageafter a voltage of a data signal is stored in the storage capacitor. Thegate electrode of the second stabilizing transistor may be coupled tothe scan line.

The pixel may include a fifth transistor coupled between a first powersource and an anode electrode of the organic light emitting diode, thefifth transistor having a gate electrode coupled to the scan line; and asixth transistor coupled between the first driving power source and thefirst electrode of the first transistor, the sixth transistor having agate electrode coupled to an ith light emitting control line.

In accordance with one or more other embodiments, a pixel includes anorganic light emitting diode; a first transistor to control an amount ofcurrent flowing from a first driving power source to a second drivingpower source, via the organic light emitting diode, based on a voltageof a first node; a second transistor coupled between a first powersource and an anode electrode of the organic light emitting diode, thesecond transistor to be turned on when a second scan signal is suppliedto a second scan line; a third transistor coupled between the first nodeand a second electrode of the first transistor, the third transistor tobe turned on when a first scan signal is supplied to a first scan line;a storage capacitor coupled between the first power source and the firstnode; and a first stabilizing transistor coupled between the first nodeand the third transistor or between the third transistor and the secondelectrode of the—first transistor, wherein the first to thirdtransistors are N-type poly-silicon semiconductor transistors and thefirst stabilizing transistor is an N-type oxide semiconductortransistor.

A gate electrode of the first stabilizing transistor is coupled to acontrol power source, and the control power source may be set to agate-on voltage during a period in which the pixel is driven at a firstdriving frequency and set to a gate-off voltage during a portion of aperiod in which the pixel is driven at a second driving frequency lowerthan the first driving frequency.

When the pixel is driven at the second driving frequency, the controlpower source may be set to the gate-off voltage after a voltage of adata signal is stored in the storage capacitor. The gate electrode ofthe first stabilizing transistor may be coupled to the first scan line.The pixel may include an second stabilizing transistor coupled betweenthe second transistor and the anode electrode of the organic lightemitting diode or between the first power source and the secondtransistor. The second stabilizing transistor may be an N-type oxidesemiconductor transistor.

A gate electrode of the second stabilizing transistor may be coupled toa control power source, and the control power source may be set to agate-on voltage during a period in which the pixel is driven at a firstdriving frequency and set to a gate-off voltage during a portion of aperiod in which the pixel is driven at a second driving frequency lowerthan the first driving frequency.

When the pixel is driven at the second driving frequency, the controlpower source may be set to the gate-off voltage after a voltage of adata signal is stored in the storage capacitor. The gate electrode ofthe second stabilizing transistor may be coupled to the second scanline. The pixel may include a first capacitor coupled between a dataline and the second electrode of the first transistor.

In accordance with one or more other embodiments, a pixel includes atleast one first transistor on a current path along which current is toflow from a first driving power source to a second driving power sourcevia an organic light emitting diode; and two or more second transistorson a current leakage path except the current path, wherein each of thesecond transistors includes: a poly-silicon semiconductor transistorcoupled to a predetermined signal line, the poly-silicon semiconductortransistor to be turned on or turned off based on a signal of the signalline; and an oxide semiconductor transistor coupled to the poly-siliconsemiconductor transistor. The oxide semiconductor transistor may be setto a turn-on state during a period in which the poly-siliconsemiconductor transistor is turned on. The oxide semiconductortransistor may be set to a turn-off state during a portion of a periodwhen the poly-silicon semiconductor transistor is turned off. Thepoly-silicon semiconductor transistor may be a P-type or N-typetransistor, and the oxide semiconductor transistor may be an N-typetransistor.

In accordance with one or more other embodiments, an organic lightemitting display device includes a plurality of pixels coupled to scanlines and data lines, wherein each of the pixels includes: at least onefirst transistor on a current path along which current flows from afirst driving power source to a second driving power source via anorganic light emitting diode; and two or more second transistors on acurrent leakage path except the current path, wherein each of the secondtransistors includes: a poly-silicon semiconductor transistor coupled toa predetermined signal line, the poly-silicon semiconductor transistorto be turned on or turned off corresponding to a signal of the signalline; and an oxide semiconductor transistor coupled to the poly-siliconsemiconductor transistor. The oxide semiconductor transistor may be setto a turn-on state during a period in which the poly-siliconsemiconductor transistor is turned on.

The oxide semiconductor transistor may be set to a turn-off state duringa portion of a period in which the poly-silicon semiconductor transistoris turned off. The poly-silicon semiconductor transistor may be a P-typeor N-type transistor. The oxide semiconductor transistor may be anN-type transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will become apparent to those of skill in the art by describingin detail exemplary embodiments with reference to the attached drawingsin which:

FIG. 1 illustrates an embodiment of an organic light emitting displaydevice;

FIGS. 2A and 2B illustrate examples of a coupling between transistors;

FIGS. 3A and 3B illustrate embodiments of a pixel;

FIG. 4 illustrates an embodiment of a method for driving a pixel;

FIG. 5 illustrates an embodiment of a pixel driven at a second drivingfrequency;

FIGS. 6A and 6B illustrate additional embodiments of a pixel;

FIGS. 7A and 7B illustrate additional embodiments of a pixel;

FIGS. 8A and 8B illustrate additional embodiments of a pixel;

FIGS. 9A and 9B illustrate additional embodiments of a pixel;

FIGS. 10A and 10B illustrate additional embodiments of a pixel;

FIGS. 11A to 11D illustrate additional embodiments of a pixel;

FIGS. 12A and 12B illustrate additional embodiments of a pixel;

FIG. 13 illustrates another embodiment of a method for driving a pixel;

FIGS. 14A and 14B illustrate additional embodiments of a pixel;

FIGS. 15A and 15B illustrate additional embodiments of a pixel;

FIG. 16 illustrates another embodiment of a method for driving a pixel;

FIGS. 17A and 17B illustrate additional embodiments of a pixel;

FIGS. 18A and 18B illustrate additional embodiments of a pixel;

FIGS. 19A and 19B illustrate additional embodiments of a pixel;

FIGS. 20A to 20D illustrate additional embodiments of a pixel;

FIGS. 21A and 21B illustrate additional embodiments of a pixel;

FIG. 22 illustrates another embodiment of a method for driving a pixel;

FIGS. 23A and 23B illustrate additional embodiments of a pixel;

FIGS. 24A and 24B illustrate additional embodiments of a pixel;

FIGS. 25A and 25B illustrate additional embodiments of a pixel; and

FIGS. 26A to 26D illustrate additional embodiments of a pixel;

DETAILED DESCRIPTION

Example embodiments are described with reference to the drawings;however, they may be embodied in different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will convey exemplary implementations to those skilled inthe art. The embodiments (or portions thereof) may be combined to formadditional embodiments

In the drawings, the dimensions of layers and regions may be exaggeratedfor clarity of illustration. It will also be understood that when alayer or element is referred to as being “on” another layer orsubstrate, it can be directly on the other layer or substrate, orintervening layers may also be present. Further, it will be understoodthat when a layer is referred to as being “under” another layer, it canbe directly under, and one or more intervening layers may also bepresent. In addition, it will also be understood that when a layer isreferred to as being “between” two layers, it can be the only layerbetween the two layers, or one or more intervening layers may also bepresent. Like reference numerals refer to like elements throughout.

When an element is referred to as being “connected” or “coupled” toanother element, it can be directly connected or coupled to the anotherelement or be indirectly connected or coupled to the another elementwith one or more intervening elements interposed therebetween. Inaddition, when an element is referred to as “including” a component,this indicates that the element may further include another componentinstead of excluding another component unless there is differentdisclosure.

FIG. 1 illustrates an embodiment of an organic light emitting displaydevice which includes a pixel unit 100, a scan driver 110, a data driver120, a light emitting driver 130, a timing controller 140, and a hostsystem 150. The host system 150 supplies image data RGB to the timingcontroller 140 through a predetermined interface, and may supply timingsignals Vsync, Hsync, DE, and CLK to the timing controller 140.

The timing controller 140 generates a scan driving control signal SCS, adata driving control signal DCS, and a light emitting driving controlsignal ECS, based on the image data RGB and the timing signals such as avertical synchronization signal Vsync, a horizontal synchronizationsignal Hsync, a data enable signal DE, and a clock signal CLK, which aresupplied from the host system 150. The scan driving control signal SCSgenerated by the timing controller 140 is supplied to the scan driver110, the data driving control signal DCS generated by the timingcontroller 140 is supplied to the data driver 120, and the lightemitting driving control signal ECS generated by the timing controller140 is supplied to the light emitting driver 130. In addition, thetiming controller 140 realigns data RGB supplied from an external sourceand supplies the realigned data RGB to the data driver 120.

The scan driving control signal SCS includes a scan start pulse andclock signals. The scan start pulse controls a first timing of a scansignal. The clock signals are used to shift the scan start pulse.

The data driving control signal DCS includes a source start pulse andclock signals. The source start pulse controls a sampling start time ofdata. The clock signals are used to control a sampling operation.

The light emitting driving control signal ECS includes a light emittingstart pulse and clock signals. The light emitting start pulse controls afirst timing of a light emitting control signal. The clock signals areused to shift the light emitting start pulse.

The scan driver 110 supplies a scan signal to scan lines S based on thescan driving control signal SCS. For example, the scan driver 110 maysequentially supply the scan signal to the scan lines S. If the scansignal is sequentially supplied to the scan lines S, pixels PXL areselected in units of horizontal lines. The scan signal is set to agate-on voltage such that transistors in the pixels PXL can be turnedon.

The data driver 120 supplies a data signal to data lines D based on thedata driving control signal DCS. The data signal supplied to the datalines D is supplied to the selected pixels PXL by the scan line. Thedata driver 120 may supply the data signal to the data lines D to besynchronized with the scan signal.

The light emitting driver 130 supplies a light emitting control signalto light emitting control lines E based on the light emitting drivingcontrol signal ECS. For example, the light emitting driver 130 maysequentially supply the light emitting control signal to the lightemitting control lines E. If the light emitting control signal issequentially supplied to the light emitting control lines E, the pixelsPXL do not emit light in units of horizontal lines. The light emittingcontrol signal is set to a gate-off voltage such that the transistors inthe pixels PXL can be turned off.

Additionally, a light emitting control signal supplied to an ith (i is anatural number) light emitting control line Ei may overlap a scan signalsupplied to an ith scan line Si. Then, pixels PXL on an ith horizontalline are set to a non-light emitting state during a period in which adata signal is supplied to pixels PXL on the ith horizontal line. Thus,undesired light may be prevented from being emitted from the pixels PXL.

In FIG. 1, the scan driver 110 and the light emitting driver 130 areillustrated as separate drivers. In one embodiment, the scan driver 100and the light emitting driver 130 may be in one driver. In addition, thescan driver 110 and/or the light emitting driver 130 may be located atdifferent sides with the pixel unit 100 therebetween.

The pixel unit 100 includes pixels PXL coupled to the data lines D, thescan lines S, and the light emitting control lines E. The pixels PXL aresupplied with a first driving power source ELVDD and a second drivingpower source ELVSS from outside.

Each of the pixels PXL is selected, when a scan signal is supplied to ascan line S coupled thereto, in order to receive a data signal from adata line D. The pixel PXL supplied with the data signal controls anamount of current flowing from the first driving power source ELVDD tothe second driving power source ELVSS, via an organic light emittingdiode, based on the data signal. At this time, the organic lightemitting diode generates light with a predetermined luminancecorresponding to the amount of current.

In FIG. 1, each pixel PXL is coupled to one scan line S, one data lineD, and one light emitting control line E. In one embodiment, the signallines S, D, and E coupled to the pixel PXL may be variously setcorresponding to pixel structures of the pixel PXL.

FIGS. 2A and 2B illustrates embodiments of coupling relationshipsbetween transistors for reducing or minimizing leakage current.Transistors in FIGS. 2A and 2B are in a pixel PXL and representtransistors located on a leakage path.

Referring to FIG. 2A, according to an embodiment, an oxide semiconductortransistor M(O) and a poly-silicon semiconductor transistor M(PP) areformed on a current leakage path of the pixel PXL. The oxidesemiconductor transistor M(O) includes a gate electrode, a sourceelectrode, and a drain electrode, and has an active layer formed of anoxide semiconductor. The oxide semiconductor may be set as an amorphousor crystalline semiconductor. The oxide semiconductor transistor M(O)may be formed as an N-type transistor. The oxide semiconductortransistor M(O) may be formed through a low temperature process and hasa lower charge mobility than the poly-silicon semiconductor transistorM(PP). The oxide semiconductor transistor M(O) has excellent off-currentcharacteristics.

The poly-silicon semiconductor transistor M(PP) includes a gateelectrode, a source electrode, and a drain electrode, and has an activelayer formed of poly-silicon. For example, the poly-siliconsemiconductor transistor M(PP) may be set as a low temperaturepoly-silicon (LTPS) transistor. The poly-silicon semiconductortransistor M(PP) may be a P-type transistor. The poly-siliconsemiconductor transistor M(PP) has a high electron mobility, andaccordingly, has fast driving characteristics.

The poly-silicon semiconductor transistor M(PP) is one of leakage pathsof the pixel PXL. In addition, the gate electrode of the poly-siliconsemiconductor transistor M(PP) may be connected to any one of signallines supplied to the pixel PXL, e.g., a scan line S. The poly-siliconsemiconductor transistor M(PP) is turned on when a scan signal issupplied to the scan line S and performs a predetermined functioncorresponding to a coupled position thereof.

The oxide semiconductor transistor M(O) is coupled to the poly-siliconsemiconductor transistor M(PP). In addition, the gate electrode of theoxide semiconductor transistor M(O) is coupled to a control power sourceVC. The oxide semiconductor transistor M(O) maintains a turn-on stateduring a period (i.e., a turn-on period) in which the poly-siliconsemiconductor transistor M(PP) is driven. If the oxide semiconductortransistor M(O) maintains the turn-on state during the period in whichthe poly-silicon semiconductor transistor M(PP) is driven, it ispossible to ensure fast driving characteristics of the poly-siliconsemiconductor transistor M(PP).

Additionally, the oxide semiconductor transistor M(O) may be set to aturn-off state during at least a portion of a period in which thepoly-silicon semiconductor transistor M(PP) is turned off. If the oxidesemiconductor transistor M(O) is turned off, it is possible to reduce orminimize leakage current flowing in the leakage path.

In one embodiment, the oxide semiconductor transistor M(O) and thepoly-silicon semiconductor transistor M(PP) may be on the leakage pathof the pixel PXL, and leakage current flowing on the leakage path isreduced or minimized with the oxide semiconductor transistor M(O). Whenthe leakage current flowing on the leakage current is reduced orminimized, an image with a desired luminance may be displayed in thepixel PXL. The oxide semiconductor transistor M(O) and the poly-siliconsemiconductor transistor M(PP), which are shown in FIG. 2A, may beapplied to various pixels PXL including P-type transistors.

Referring to FIG. 2B, according to an embodiment, an oxide semiconductortransistor M(O) and a poly-silicon semiconductor transistor M(PN) are onthe current leakage path of the pixel PXL. The oxide semiconductortransistor M(O) includes a gate electrode, a source electrode, and adrain electrode, and has an active layer of an oxide semiconductor. Theoxide semiconductor may be set as an amorphous or crystallinesemiconductor. The oxide semiconductor transistor M(O) may be an N-typetransistor.

The oxide semiconductor transistor M(O) may be formed through a lowtemperature process and has a lower charge mobility than thepoly-silicon semiconductor transistor M(PP). The oxide semiconductortransistor M(O) has excellent off-current characteristics.

The poly-silicon semiconductor transistor M(PN) includes a gateelectrode, a source electrode, and a drain electrode, and has an activelayer formed of poly-silicon. For example, the poly-siliconsemiconductor transistor M(PN) may be set as an LTPS transistor. Thepoly-silicon semiconductor transistor M(PN) may be formed as an N-typetransistor. The poly-silicon semiconductor transistor M(PN) has a highelectron mobility, and accordingly, has fast driving characteristics.

The poly-silicon semiconductor transistor M(PN) is on any one of leakagepaths of the pixel PXL. In addition, the gate electrode of thepoly-silicon semiconductor transistor M(PN) may be connected to any oneof signal lines supplied to the pixel PXL, e.g., a scan line S. Thepoly-silicon semiconductor transistor M(PN) is turned on when a scansignal is supplied to the scan line S, and performs a predeterminedfunction corresponding to a coupled position thereof.

The oxide semiconductor transistor M(O) is coupled to the poly-siliconsemiconductor transistor M(PN). In addition, the gate electrode of theoxide semiconductor transistor M(O) is coupled to a control power sourceVC. The oxide semiconductor transistor M(O) maintains a turn-on stateduring a period (i.e., a turn-on period) in which the poly-siliconsemiconductor transistor M(PN) is driven. If the oxide semiconductortransistor M(O) maintains the turn-on state during the period in whichthe poly-silicon semiconductor transistor M(PN) is driven, it ispossible to ensure fast driving characteristics of the poly-siliconsemiconductor transistor M(PN).

The oxide semiconductor transistor M(O) may be set to a turn-off stateduring at least a portion of a period in which the poly-siliconsemiconductor transistor M(PN) is turned off. If the oxide semiconductortransistor M(O) is turned off, it is possible to reduce or minimizeleakage current flowing in the leakage path.

In one embodiment, the oxide semiconductor transistor M(O) and thepoly-silicon semiconductor transistor M(PN) may be on the leakage pathof the pixel PXL, and leakage current flowing on the leakage path isreduced or minimized using the oxide semiconductor transistor M(O). Whenthe leakage current flowing on the leakage current is reduced orminimized, an image with a desired luminance can be displayed in thepixel PXL. The oxide semiconductor transistor M(O) and the poly-siliconsemiconductor transistor M(PN), which are shown in FIG. 2B, may beapplied to various pixels PXL including N-type transistors.

FIGS. 3A and 3B illustrates an embodiment of a pixel PXL on an ithhorizontal line and coupled to an mth data line Dm. Referring to FIG.3A, the pixel PXL includes an organic light emitting diode OLED and apixel circuit 2001 for controlling the amount of current supplied to theorganic light emitting diode OLED. An anode electrode of the organiclight emitting diode OLED is coupled to the pixel circuit 2001, and acathode electrode of the organic light emitting diode OLED is coupled toa second driving power source ELVSS. The organic light emitting diodeOLED generates light with a predetermined luminance corresponding to theamount of current supplied from the pixel circuit 2001.

The pixel circuit 2001 controls the amount of current flowing from afirst driving power source ELVDD to the second driving power sourceELVSS via the organic light emitting diode OLED. To this end, the pixelcircuit 2001 includes first to seventh transistors M1 to M7, a firststabilizing transistor MS1, and a storage capacitor Cst.

A first electrode of the first transistor (or driving transistor) M1 iscoupled to a first node N1, and a second electrode of the firsttransistor M1 is coupled to the anode electrode of the organic lightemitting diode OLED via the seventh transistor M7. In addition, a gateelectrode of the first transistor M1 is coupled to a second node N2. Thefirst transistor M1 controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS via the organic light emitting diode OLED, corresponding to avoltage of the second node N2. To this end, the first driving powersource ELVDD is set to a higher voltage than the second driving powersource ELVSS.

The second transistor M2 is coupled between a data line Dm and the firstnode N1. In addition a gate electrode of the second transistor M2 iscoupled to an ith first scan line S1 i. The second transistor M2 isturned on when a first scan signal is supplied to the ith first scanline S1 i in order to allow the data line Dm and the first node N1 to beelectrically coupled to each other.

The third transistor M3 is coupled between the second electrode of thefirst transistor M1 and the second node N2. In addition, a gateelectrode of the third transistor M3 is coupled to the ith first scanline S1 i and is turned on when the first scan signal is supplied to theith first scan line S1 i.

The first stabilizing transistor MS1 is coupled between the thirdtransistor M3 and the second node N2. In addition, a gate electrode ofthe first stabilizing transistor MS1 is coupled to a control powersource VC. The first stabilizing transistor MS1 is turned on or turnedoff corresponding to a voltage of the control power source VC. The firststabilizing transistor MS1 is an oxide semiconductor transistor.

The control power source VC is set to a gate-on voltage such that thefirst stabilizing transistor MS1 is turned on when the pixel PXL isdriven at a first driving frequency (e.g., a normal driving frequency).When the pixel PXL is driven at the first driving frequency, the firststabilizing transistor MS1 maintains a turn-on state.

The control power source VC is set to a gate-off voltage during a periodin which the pixel PXL is driven at a second driving frequency lowerthan the first driving frequency (i.e., low frequency driving). Thefirst stabilizing transistor MS1 maintains a turn-off state during aperiod in which the pixel PXL is driven at the second driving frequency.If the first stabilizing transistor MS1 is turned off, leakage currentfrom the second node N2 is minimized, and accordingly, an image with adesired luminance can be implemented in the pixel PXL during the periodin which the pixel PXL is driven at the second driving frequency.

In FIG. 3A, the first stabilizing transistor MS1 is coupled between thethird transistor M3 and the second node N2. In one embodiment, as shownin FIG. 3B, the first stabilizing transistor MS1 may be coupled betweenthe second electrode of the first transistor M1 and the third transistorM3.

The fourth transistor M4 is coupled between the second node N2 and afirst power source Vint. A gate electrode of the fourth transistor M4 iscoupled to an ith second scan line S2 i. The fourth transistor M4 isturned on when a second scan signal is supplied to the ith second scanline S2 i to supply a voltage of the first power source Vint to thesecond node N2. The first power source Vint is set to a lower voltagethan a data signal supplied to the data line Dm. The second scan signalsupplied to the ith second scan line S2 i is supplied earlier than thefirst scan signal supplied to the ith first scan line S1 i. Thus, theith second scan line S2 i may be set as an (i−1)th first scan line S1i−1.

The fifth transistor M5 is coupled between the anode electrode of theorganic light emitting diode OLED and the first power source Vint. Agate electrode of the fifth transistor M5 is coupled to an ith thirdscan line S3 i. The fifth transistor M5 is turned on when a third scansignal is supplied to the ith third scan line S3 i to supply the voltageof the first power source Vint to the anode electrode of the organiclight emitting diode OLED. The third scan signal supplied to the iththird scan line S3 i overlaps a light emitting control signal suppliedto a light emitting control line Ei. Accordingly, the ith third scanline S3 i may be set as the ith first scan line S1 i or the ith secondscan line S2 i.

If the voltage of the first power source Vint is supplied to the anodeelectrode of the organic light emitting diode OLED, a parasiticcapacitor (organic capacitor Coled) of the organic light emitting diodeOLED is discharged. If the organic capacitor Coled is discharged, theblack expression ability of the pixel PXL is improved.

For example, a predetermined voltage is charged in the organic capacitorColed, corresponding to a current supplied from the pixel circuit 2001,during a previous frame period. If the organic capacitor Coled ischarged, the organic light emitting diode OLED may easily emit lighteven at a low current.

A black data signal may be supplied to the pixel circuit 2001 in acurrent frame period. When the black data signal is supplied, the pixelcircuit 2001 is to ideally supply no current to the organic lightemitting diode OLED. However, the pixel circuit 2001 formed with thetransistors supplies a predetermined leakage current to the organiclight emitting diode OLED even when the black data signal is supplied.At this time, if the organic capacitor Coled is in a charge-state, theorganic light emitting diode OLED may minutely emit light. Thus, theblack expression ability of the pixel PXL is deteriorated.

On the other hand, if the organic capacitor Coled is discharged by thefirst power source Vint, the organic light emitting diode OLED is set toa non-light emitting state by leakage current. That is, in oneembodiment, the organic capacitor Coled is discharged using the firstpower source Vint. Thus, the black expression ability of the pixel PXLcan be improved.

The sixth transistor M6 is coupled between the first driving powersource ELVDD and the first node N1. In addition, a gate electrode of thesixth transistor M6 is coupled to an ith light emitting control line Ei.The sixth transistor M6 is turned off when a light emitting controlsignal is supplied to the ith light emitting control line Ei, and turnedon when the light emitting control signal is not supplied.

The seventh transistor M7 is coupled between the first transistor M1 andthe anode electrode of the organic light emitting diode OLED. Inaddition, a gate electrode of the seventh transistor M7 is coupled tothe ith light emitting control line Ei. The seventh transistor M7 isturned off when the light emitting control signal is supplied to the ithlight emitting control line Ei, and turned on when the light emittingcontrol signal is not supplied.

The storage capacitor Cst is coupled between the first driving powersource ELVDD and the second node N2. The storage capacitor Cst charges avoltage corresponding to a data signal and a threshold voltage of thefirst transistor M1.

In the pixel PXL of the present embodiment, the first to seventhtransistors T1 to T7 are P-type poly-silicon semiconductor transistors.Particularly, transistors M1, M6, and M7 on a current supply path forsupplying current to the organic light emitting diode OLED are P-typepoly-silicon semiconductor transistors. If the transistors M1 to M7 arepoly-silicon semiconductor transistors, fast driving characteristics canbe ensured.

In addition, the first stabilizing transistor MS1 is an N-type oxidesemiconductor transistor. If the first stabilizing transistor MS1 is anoxide semiconductor transistor, the leakage current from the second nodecan be reduced or minimized. Accordingly, an image with a desiredluminance can be displayed in the pixel unit 100.

FIG. 4 illustrates an embodiment of a method for driving the pixel inFIGS. 3A and 3B. In FIG. 4, it is assumed that the ith second scan lineS2 i is set to the (i−1)th first scan line S1 i−1 and the ith third scanline S3 i is set to the ith first scan line S1 i. In addition, thedriving method of FIG. 4 corresponds to the first driving frequency, andit is assumed that the first stabilizing transistor MS1 is set to theturn-on state.

Referring to FIG. 4, during a first period T1, the light emittingcontrol signal is supplied to the ith light emitting control line Ei,and the second scan signal is supplied to the ith second scan line S2 i.If the light emitting control signal is supplied to the ith lightemitting control line Ei, sixth transistor M6 and the seventh transistorM7 are turned off.

If the sixth transistor M6 is turned off, the first driving power sourceELVDD and the first node are electrically interrupted. If the seventhtransistor M7 is turned off, the first transistor M1 and the organiclight emitting diode OLED are electrically interrupted. Therefore, thepixel PXL is set to the non-light emitting state during a period inwhich the light emitting control signal is supplied to the ith lightemitting control line Ei, i.e., the first period T1 and a second periodT2.

If the second scan signal is supplied to the ith second scan line S2 i,the fourth transistor M4 is turned on. If the fourth transistor M4 isturned on, the voltage of the first power source Vint is supplied to thesecond node N2.

During the second period T2, the first scan signal is supplied to theith first scan line S1 i. If the first scan signal is supplied to theith first scan line S1 i, the second transistor M2, the third transistorM3, and the fifth transistor M5 are turned on.

If the fifth transistor M5 is turned on, the voltage of the first powersource Vint is supplied to the anode electrode of the organic lightemitting diode OLED. If the voltage of the first power source Vint issupplied to the anode electrode of the organic light emitting diodeOLED, the organic capacitor Coled is discharged. Accordingly, the blackexpression ability of the pixel PXL is improved.

If the third transistor M3 is turned on, the second electrode of thefirst transistor M1 and the second node N2 are electrically coupled toeach other. For example, the first transistor M1 is diode-coupled. Here,during the second period T2, the first stabilizing transistor MS1 is setto the turn-on state. Accordingly, the electrical coupling between thesecond electrode of the first transistor M1 and the second node N2 iscontrolled corresponding to turn-on and turn-off of the third transistorM3.

If the second transistor M2 is turned on, the data signal from the dataline Dm is supplied to the first node N1. At this time, since the secondnode N2 is initialized to the voltage of the first power source Vint,which is lower than the data signal, the first transistor M1 is turnedon.

If the first transistor M1 is turned on, the data signal supplied to thefirst node N1 is supplied to the second node N2 via the diode-coupledfirst transistor M1. At this time, the voltage corresponding to the datasignal and the threshold voltage of the first transistor M1 is appliedto the second node N2. During the second period T2, the storagecapacitor Cst stores the voltage of the second node N2.

During a third period T3, the supply of the light emitting controlsignal to the ith light emitting control line Ei is stopped. If thesupply of the light emitting control signal to the ith light emittingcontrol line Ei is stopped, the sixth transistor M6 and the seventhtransistor M7 are turned on.

If the sixth transistor M6 is turned on, the first driving power sourceELVDD and the first node N1 are electrically coupled to each other. Ifthe seventh transistor M7 is turned on, the second electrode of thefirst transistor M1 and the anode electrode of the organic lightemitting diode OLD are electrically coupled to each other. At this time,the first transistor M1 controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS, via the organic light emitting diode OLED, based on the voltageapplied to the second node N2.

As described above, the pixel PXL generates light with a predeterminedluminance while repeating the first to third periods T1 to T3 during aperiod in which the pixel PXL is driven at the first driving frequency.In addition, the first stabilizing transistor MS1 maintains the turn-onstate during the period in which the pixel PXL is driven at the firstdriving frequency. Accordingly, the pixel PXL can be stably driven.

FIG. 5 illustrates an embodiment when the pixel of FIGS. 3A and 3B isdriven at the second driving frequency. Referring to FIG. 5, the lowfrequency driving means a driving method of maintaining light emissionof the pixel PXL while maintaining a voltage of the data signal for apredetermined time, after the data signal is supplied to the pixel PXL.For example, when a still image is displayed in the pixel unit 100, adriving frequency of the organic light emitting display device may bechanged from the first driving frequency to the second drivingfrequency. If the organic light emitting display device is driven at thesecond driving frequency, the number of times of supplying the datasignal is decreased. Accordingly, power consumption is reduced.

An operating process of the pixel PXL will be described. During firstand second periods T1 and T2 in which the data signal is supplied to thepixels PXL, the voltage of the control power source VC is set such thatthe first stabilizing transistor MS1 is turned on. Then, the voltage ofthe data signal is normally supplied to each of the pixels PXL.

After the data signal is supplied to each of the pixels PXL, the voltageof the control power source VC is set such that first stabilizingtransistor MS1 is turned off. Accordingly, the first stabilizingtransistor MS1 is turned off.

If the first stabilizing transistor MS1 is turned off, the leakagecurrent from the second node N2 can be reduced or minimized during aperiod in which the pixel PXL emits light. Accordingly, light with adesired luminance can be generated from the pixel PXL. Particularly, thefirst stabilizing transistor MS1 is formed as an oxide semiconductortransistor having excellent off-current characteristics. Accordingly,the leakage current from the second node N2 can be reduced or minimized.

FIGS. 6A and 6B illustrate additional embodiments of a pixel PXLaccording to the another embodiment of the present disclosure includes apixel circuit 2001′ and an organic light emitting diode OLED. An anodeelectrode of the organic light emitting diode OLED is coupled to thepixel circuit 2001′, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2001′.

The pixel circuit 2001′ controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS, via the organic light emitting diode OLED, based on the datasignal. The pixel circuit 2001′ includes a first stabilizing transistorMS1′ on a current path between the second node N2 and the firsttransistor M1. The first stabilizing transistor MS1′ may be between thethird transistor M3 and the second node N2 or between the secondelectrode of the first transistor M1 and the third transistor M3.

A gate electrode of the first stabilizing transistor MS1′ is coupled tothe ith light emitting control line Ei. The first stabilizing transistorMS1′ is turned o when the light emitting control signal is supplied tothe ith light emitting control line Ei, and turned off when the lightemitting control signal is not supplied.

An operating process of the pixel PXL will be described with referenceto FIGS. 4, 6A, and 6B. During the first period T1, the light emittingcontrol signal is supplied to the ith light emitting control line Ei,and the second scan signal is supplied to the ith second scan line S2 i.

If the light emitting control signal is supplied to the ith lightemitting control line Ei, the sixth transistor M6 and the seventhtransistor M7 are turned off. Accordingly, the pixel PXL is set to thenon-light emitting state. If the second scan signal is supplied to theith second scan line S2 i, the fourth transistor M4 is turned on.Accordingly, the second node N2 is initialized to the voltage of thefirst power source Vint. In addition, if the light emitting controlsignal is supplied to the ith light emitting control line Ei, the firststabilizing transistor MS1′ is turned on.

During the second period T2, the first scan signal is supplied to theith first scan line S1 i. If the first scan signal is supplied to theith first scan line S1 i, the second transistor M2, the third transistorM3, and the fifth transistor M5 are turned on.

If the fifth transistor M5 is turned on, the voltage of the first powersource Vint is supplied to the anode electrode of the organic lightemitting diode OLED. Accordingly, the organic capacitor Coled isdischarged.

If the third transistor M3 is turned on, the second electrode of thefirst transistor M1 and the second node N2 are electrically coupled toeach other. That is, the first transistor M1 is diode-coupled. The firststabilizing transistor MS1′ is set to the turn-on state during thesecond period T2. Accordingly, the electrical coupling between thesecond electrode of the first transistor M1 and the second node N2 iscontrolled corresponding to turn-on and turn-off of the third transistorM3.

If the second transistor M2 is turned on, the data signal from the dataline Dm is supplied to the first node N1. Then, the data signal suppliedto the first node N1 is supplied to the second node N2 via thediode-coupled first transistor M1. At this time, the voltagecorresponding to the data signal and the threshold voltage of the firsttransistor M1 is applied to the second node N2. During the second periodT2, the voltage of the second node N2 is stored in the storage capacitorCst.

During the third period T3, the supply of the light emitting controlsignal to the ith light emitting control line Ei is stopped. If thesupply of the light emitting control signal to the ith light emittingcontrol line Ei is stopped, the sixth transistor M6 and the seventhtransistor M7 are turned on. If supply of the light emitting controlsignal to the ith light emitting control line Ei is stopped, firststabilizing transistor MS1′ is turned off.

If the sixth transistor M6 and the seventh transistor M7 are turned on,there is formed a current path along which current flows from the firstdriving power source ELVDD to the second driving power source ELVSS viathe sixth transistor M6, the first transistor M1, the seventh transistorM7, and the organic light emitting diode OLED. At this time, the firsttransistor M1 controls the amount of current flowing from the firstdriving power source ELVDD to the second driving power source ELVSS viathe organic light emitting diode OLED, corresponding to the voltageapplied to the second node N2.

Meanwhile, during the third period in which the pixel PXL emits light,the first stabilizing transistor MS1′ maintains the turn-off state. Ifthe first stabilizing transistor MS1′ is turned off, the leakage currentfrom the second node N2 can be reduced or minimized during the period inwhich the pixel PXL emits light, and accordingly, light with a desiredluminance can be generated from the pixel PXL.

FIGS. 7A and 7B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2002 and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is coupledto the pixel circuit 2002, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2002.

The pixel circuit 2002 controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS via the organic light emitting diode OLED, corresponding to thedata signal.

The pixel circuit 2002 includes a second stabilizing transistor MS2 on acurrent path between the second node N2 and the first power source Vint.For example, the second stabilizing transistor MS2 may be between thesecond node N2 and the fourth transistor M4 or between the fourthtransistor M4 and the first power source Vint.

A gate electrode of the second stabilizing transistor MS2 is coupled tothe control power source VC. The second stabilizing transistor MS2maintains the turn-on state when the organic light emitting displaydevice is driven at the first driving frequency. An operating process ofthe pixel PXL may be the same as described with reference to FIGS. 3A to4.

Meanwhile, the second stabilizing transistor MS2 is turned off during aperiod in which the organic light emitting display device is driven atthe second driving frequency, i.e., a period in which the organic lightemitting display device is driven at a low frequency. At this time, thevoltage of the control power source VC is set such that the secondstabilizing transistor MS2 is turned on during the first and secondperiods T1 and T2 in which the data signal is supplied to the pixels PXLas shown in FIG. 5. Then, the voltage of the data signal is normallysupplied to each of the pixels PXL.

After the data signal is supplied to each of the pixels PXL, the voltageof the control power source VC is set such that the second stabilizingtransistor MS2 is turned off. Accordingly, the second stabilizingtransistor MS2 is turned off.

If the second stabilizing transistor MS2 is turned off, leakage currentbetween the second node N2 and the first power source Vint is reduced orminimized. Accordingly, an image with a desired luminance can bedisplayed. In an embodiment of the present disclosure, the secondstabilizing transistor MS2 is formed as an oxide semiconductortransistor. Accordingly, the leakage current can be reduced orminimized.

Meanwhile, in FIGS. 7A and 7B, it has been illustrated that the firststabilizing transistor MS1 or MS1′ is removed as compared with FIGS. 3A,3B, 6A, and 6B, but the present disclosure is not limited thereto. Forexample, the first stabilizing transistor MS1 or MS1′ may be added tothe pixel PXL of FIGS. 7A and 7B.

FIGS. 8A and 8B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2002′ and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is coupledto the pixel circuit 2002′, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2002′.

The pixel circuit 2002′ controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS via the organic light emitting diode OLED, corresponding to thedata signal.

The pixel circuit 2002′ includes a second stabilizing transistor MS2′ ona current path between the second node N2 and the first power sourceVint. For example, the second stabilizing transistor MS2′ may be betweenthe second node N2 and the fourth transistor M4 or between the fourthtransistor M4 and the first power source Vint.

A gate electrode of the second stabilizing transistor MS2′ is coupled tothe ith light emitting control line Ei. The second stabilizingtransistor MS2′ is turned on when the light emitting control signal issupplied to the ith light emitting control line Ei, and turned off whenthe light emitting control signal is not supplied. An operating processof the pixel PXL may be the same as described with reference to FIGS. 4,6A, and 6B.

If the second stabilizing transistor MS2′ is turned off, leakage currentbetween the second node N2 and the first power source Vint is reduced orminimized. Accordingly, an image with a desired luminance can bedisplayed. In the present embodiment, the second stabilizing transistorMS2′ is an oxide semiconductor transistor, Accordingly, the leakagecurrent can be minimized.

Meanwhile, in FIGS. 8A and 8B, it has been illustrated that the firststabilizing transistor MS1 is removed as compared with FIGS. 3A, 3B, 6A,and 6B, but the present disclosure is not limited thereto. For example,the first stabilizing transistor MS1 may be added to the pixel PXL ofFIGS. 8A and 8B.

FIGS. 9A and 9B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2003 and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is connectedto the pixel circuit 2003, and a cathode electrode of the organic lightemitting diode OLED is connected to the second driving power sourceELVSS. The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2003.

The pixel circuit 2003 controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS via the organic light emitting diode OLED, corresponding to thedata signal.

The pixel circuit 2003 includes a third stabilizing transistor MS3 on acurrent path between the anode electrode of the organic light emittingdiode OLED and the first power source Vint. For example, the thirdstabilizing transistor MS3 may be between the anode electrode of theorganic light emitting diode OLED and the fifth transistor M5 or betweenthe fifth transistor M5 and the first power source Vint.

A gate electrode of the third stabilizing transistor MS3 is coupled tothe control power source VC. The third stabilizing transistor MS3maintains the turn-on state when the organic light emitting displaydevice is driven at the first driving frequency. An operating process ofthe pixel PXL may be the same as described with reference to FIGS. 3A to4.

Meanwhile, the third stabilizing transistor MS3 is turned off during aperiod in which the organic light emitting display device is driven atthe second driving frequency, i.e., a period in which the organic lightemitting display device is driven at a low frequency. At this time, thevoltage of the control power source VC is set such that the thirdstabilizing transistor is turned on during the first and second periodsT1 and T2 in which the data signal is supplied to the pixels PXL. Then,the voltage of the data signal is normally supplied to each of thepixels PXL.

After the data signal is supplied to each of the pixels PXL, the voltageof the control power source VC is set such that the third stabilizingtransistor MS3 is turned off. Accordingly, the third stabilizingtransistor MS3 is turned off.

If the third stabilizing transistor MS3 is turned off, leakage currentbetween the anode electrode of the organic light emitting diode OLED andthe first power source Vint is reduced or minimized. Accordingly, animage with a desired luminance can be displayed. In the presentembodiment, the third stabilizing transistor MS3 is an oxidesemiconductor transistor. Accordingly, the leakage current can bereduced or minimized.

In FIGS. 9A and 9B, it has been illustrated that the first stabilizingtransistor MS1 is removed as compared with FIGS. 3A, 3B, 6A, and 6B, butthe present disclosure is not limited thereto. For example, the firststabilizing transistor MS1 may be added to the pixel PXL of FIGS. 9A and9B.

FIGS. 10A and 10B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2003′ and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is coupledto the pixel circuit 2003′, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2003′.

The pixel circuit 2003′ includes a third stabilizing transistor MS3′ ona current path between the anode electrode of the organic light emittingdiode OLED and the first power source Vint. For example, the thirdstabilizing transistor MS3′ may be between the anode electrode of theorganic light emitting diode OLED and the fifth transistor M5 or betweenthe fifth transistor M5 and the first power source Vint.

A gate electrode of the third stabilizing transistor MS3′ is coupled tothe ith light emitting control line Ei. The third stabilizing transistorMS3′ is turned on when the light emitting control signal is supplied tothe ith light emitting control line Ei, and turned off when the lightemitting control signal is not supplied. An operating process of thepixel PXL is the same as described with reference to FIGS. 4, 6A, and6B.

If the third stabilizing transistor MS3′ is turned off, leakage currentbetween the anode electrode of the organic light emitting diode OLED andthe first power source Vint is reduced or minimized. Accordingly, animage with a desired luminance can be displayed. In the presentembodiment, the third stabilizing transistor MS3′ is an oxidesemiconductor transistor. Thus, leakage current can be reduced orminimized.

Meanwhile, in FIGS. 10A and 10B, it has been illustrated that the firststabilizing transistor MS1 is removed as compared with FIGS. 3A, 3B, 6A,and 6B, but the present disclosure is not limited thereto. For example,the first stabilizing transistor MS1 may be added to the pixel PXL ofFIGS. 10A and 10B.

In the present embodiment, at least one transistor among the firststabilizing transistor MS1 or MS1′, the second stabilizing transistorMS2 or MS2′, and the third stabilizing transistor MS3 or MS3′ may beformed in the pixel PXL. For example, as shown in FIGS. 11A to 11D, thefirst stabilizing transistor MS1 or MS1′, the second stabilizingtransistor MS2 or MS2′, and the third stabilizing transistor MS3 or MS3′may be formed in the pixel PXL.

If the first stabilizing transistor MS1 or MS1′, the second stabilizingtransistor MS2 or MS2′, and the third stabilizing transistor MS3 or MS3′are formed in the pixel PXL, leakage current is reduced or minimizedduring the third period T3 in which the organic light emitting diodeOLED emits light. Accordingly, an image with a desired luminance can bedisplayed. Particularly, the first stabilizing transistor MS1 or MS1′,the second stabilizing transistor MS2 or MS2′, and the third stabilizingtransistor MS3 or MS3′ are formed as oxide semiconductor transistors, animage with a desired luminance can be stably displayed even when thepixel PXL is driven at a low frequency.

FIGS. 12A and 12B illustrate additional embodiments of a pixel PXL whichincludes an organic light emitting diode OLED and a pixel circuit 2004for controlling the amount of current supplied to the organic lightemitting diode OLED. An anode electrode of the organic light emittingdiode OLED is coupled to the pixel circuit 2004, and a cathode electrodeof the organic light emitting diode OLED is coupled to the seconddriving power source ELVSS. The organic light emitting diode OLEDgenerates light with a predetermined luminance corresponding to theamount of current supplied from the pixel circuit 2004.

The pixel circuit 2004 controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS via the organic light emitting diode OLED, corresponding to thedata signal. To this end, the pixel circuit 2004 includes eleventh tothirteenth transistors M11 to M13, a fourth stabilizing transistor MS4,and a storage capacitor Cst.

A first electrode of the eleventh transistor (or driving transistor) M11is coupled to the first driving power source ELVDD via the thirteenthtransistor M13, and a second electrode of the eleventh transistor M11 iscoupled to the anode electrode of the organic light emitting diode OLED.In addition, a gate electrode of the eleventh transistor M11 is coupledto an eleventh node N11. The eleventh transistor M11 controls the amountof current flowing the first driving power source ELVDD to the seconddriving power source ELVSS via the organic light emitting diode OLED,corresponding to a voltage of the eleventh node N11.

The twelfth transistor M12 is coupled between a data line D and theeleventh node N11. In addition, a gate electrode of the twelfthtransistor M12 is coupled to a scan line S. The twelfth transistor M12is turned on when a scan signal is supplied to the scan line S.

The thirteenth transistor M13 is coupled between the first driving powersource ELVDD and the first electrode of the eleventh transistor M11. Inaddition, a gate electrode of the thirteenth transistor M13 is coupledto a light emitting control line E. The thirteenth transistor M13 isturned off when a light emitting control signal is supplied to the lightemitting control line E, and turned on when the light emitting controlsignal is not supplied.

The fourth stabilizing transistor MS4 is located on a current pathbetween the data line D and the eleventh node N11. For example, thefourth stabilizing transistor MS4 may be located between the twelfthtransistor M12 and the eleventh node N11 or between the data line D andthe twelfth transistor M12.

A gate electrode of the fourth stabilizing transistor MS4 is coupled tothe control power source VC. The fourth stabilizing transistor MS4maintains the turn-on state when the organic light emitting displaydevice is driven at the first driving frequency. Also, the fourthstabilizing transistor MS4 is turned off after the organic lightemitting display device is driven at the second driving frequency, and avoltage corresponding to a data signal is charged in the storagecapacitor Cst.

Meanwhile, the fourth stabilizing transistor MS4 is an oxidesemiconductor transistor. Thus, if the fourth stabilizing transistor MS4is turned off, leakage current between the data line D and the eleventhnode N11 is reduced or minimized. Accordingly, an image with a desiredluminance can be implemented in the pixel PXL.

The storage capacitor Cst is coupled between the eleventh node N11 andthe anode electrode of the organic light emitting diode OLED. Thestorage capacitor Cst stores a voltage corresponding to the data signal.

Meanwhile, in the above-described pixel PXL according to the presentembodiment, the eleventh to thirteenth transistors M11 to M13 are N-typepoly-silicon semiconductor transistors. As described above, if thetransistors M11 to M13 are formed as poly-silicon semiconductortransistors, fast driving characteristics can be ensured.

FIG. 13 illustrate another embodiment of a method for driving a pixel,which, for example may be the pixel PXL shown in FIGS. 12A and 12B.Referring to FIG. 13, first, the light emitting control signal issupplied to the light emitting control line E such that the thirteenthtransistor M13 is turned off. If the thirteenth transistor M13 is turnedoff, the first driving power source ELVDD and eleventh transistor M11are electrically interrupted, and accordingly, the pixel PXL is set tothe non-light emitting state.

After that, the scan signal is supplied to the scan line S such that thetwelfth transistor M12 is turned on. If the twelfth transistor M12 isturned on, the data line D and the eleventh node N11 are electricallycoupled to each other. Then, the data signal from the data line D issupplied to the eleventh node N11. Accordingly, a voltage correspondingto the data signal is stored in the storage capacitor Cst.

The supply of the light emitting control signal to the light emittingcontrol line E is stopped after the voltage corresponding to the datasignal is stored in the storage capacitor Cst. If the supply of thelight emitting control signal to the light emitting control line E isstopped, the thirteenth transistor M13 is turned on. If the thirteenthtransistor M13 is turned on, the first driving power source ELVDD andthe eleventh transistor M11 are electrically coupled to each other.

At this time, the eleventh transistor M11 controls the amount of currentflowing from the first driving power source ELVDD to the second drivingpower source ELVSS, via the organic light emitting diode OLED, based ona voltage of the eleventh node N11.

As described above, the pixel of the present embodiment generates lightwith a predetermined luminance while repeating the above-describedprocess during a period in which the organic light emitting displaydevice is driven at the first driving frequency. In addition, the fourthstabilizing transistor MS4 maintains the turn-on state during the periodin which the organic light emitting display device is driven at thefirst driving frequency. Accordingly, the pixel PXL can be stablydriven.

Additionally, during the organic light emitting display device is drivenat the second driving frequency, the voltage corresponding to the datasignal is charged in the storage capacitor Cst of each of the pixelsPXL, and the control power source VC is set to a gate-off voltage. Then,the fourth stabilizing transistor MS4 in each of the pixels PXL isturned off. Accordingly, leakage current between the data line D and theeleventh node N11 can be reduced or minimized. Thus, the pixel PXL canstably generate light with a desired luminance even when the organiclight emitting display device is driven at the second driving frequency.

Meanwhile, in the present embodiment, the driving method of the pixelPXL of FIGS. 12A and 12B is not limited to that of FIG. 13. For example,the pixel PXL of FIGS. 12A and 12B may be driven with various types ofdriving waveforms currently known in the art.

FIGS. 14A and 14B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2004′ and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is coupledto the pixel circuit 2004′, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the current supplied from thepixel circuit 2004′.

The pixel circuit 2004′ controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS, via the organic light emitting diode OLED, based on the datasignal.

The pixel circuit 2004′ includes a fourth stabilizing transistor MS4′located on a current path between the data line D and the eleventh nodeN11. For example, the fourth stabilizing transistor MS4′ may be locatedbetween the twelfth transistor M12 and the eleventh node N11 or betweenthe data line D and the twelfth transistor M12.

A gate electrode of the fourth stabilizing transistor MS4′ is coupled tothe scan line S. The fourth stabilizing transistor MS4′ is turned onwhen the scan signal is supplied to the scan line S and turned off whenthe scan signal is not supplied. That is, the fourth stabilizingtransistor MS4′ is turned on or turned off simultaneously with thetwelfth transistor M12.

An operating process of the pixel PXL will be described with referenceto FIGS. 13, 14A, and 14B. First, the light emitting control signal issupplied to the light emitting control line E such that the thirteenthtransistor M13 is turned off. If the thirteenth transistor M13 is turnedoff, the pixel PXL is set to the non-light emitting state.

After that, the scan signal is supplied to the scan line S such that thetwelfth transistor M12 and the fourth stabilizing transistor MS4′ areturned on. If the twelfth transistor m12 and the fourth stabilizingtransistor MS4′ are turned on, the data line D and the eleventh node N11are electrically coupled to each other. Then, the data signal from thedata line D is supplied to the eleventh node N11. Accordingly, a voltagecorresponding to the data signal is stored in the storage capacitor Cst.

The supply of the light emitting control signal to the light emittingcontrol line E is stopped after the voltage corresponding to the datasignal is stored in the storage capacitor Cst. If the supply of thelight emitting control signal to the light emitting control line E isstopped, the thirteenth transistor M13 is turned on. If the thirteenthtransistor M13 is turned on, the first driving power source ELVDD andthe eleventh transistor M11 are electrically coupled to each other.

At this time, the eleventh transistor M11 controls the amount of currentflowing from the first driving power source ELVDD to the second drivingpower source ELVSS, via the organic light emitting diode OLED,corresponding to a voltage of the eleventh node N11.

Meanwhile, the fourth stabilizing transistor MS4′ maintains the turn-offstate during a period in which the pixel PXL emits light. If the fourthstabilizing transistor MS4′ is turned off, leakage current between thedata line D and the eleventh node N11 can be reduced or minimized duringthe period in which the pixel PXL emits light. Accordingly, light with adesired luminance can be generated from the pixel PXL.

FIGS. 15A and 15B illustrates additional embodiments of a pixel PXLlocated on an ith horizontal line and coupled to an mth data line Dm.Referring to FIGS. 15A and 15B, the pixel PXL includes an organic lightemitting diode OLED and a pixel circuit 2005 for controlling the amountof current supplied to the organic light emitting diode OLED. An anodeelectrode of the organic light emitting diode OLED. Is coupled to thepixel circuit 2005, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2005.

The pixel circuit 2005 controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS via the organic light emitting diode OLED, corresponding to a datasignal. To this end, the pixel circuit 2005 includes twenty-first totwenty-sixth transistors M21 to M26, a fifth stabilizing transistor MS5,and a storage capacitor Cst.

A first electrode of the twenty-first transistor (driving transistor)M21 is coupled to the first driving power source ELVDD via thetwenty-sixth transistor M26, and a second electrode of the twenty-firsttransistor M21 is coupled to the anode electrode of the organic lightemitting diode OLED. In addition, a gate electrode of the twenty-firsttransistor M21 is coupled to a twenty-first node N21. The twenty-firsttransistor M21 controls the amount of current flowing from the firstdriving power source ELVDD to the second driving power source ELVSS viathe organic light emitting diode OLED, corresponding to a voltage of thetwenty-first node N21.

The twenty-second transistor M22 is coupled between a data line Dm and atwenty-second node N22. In addition, a gate electrode of thetwenty-second transistor M22 is coupled to an ith scan line Si. Thetwenty-second transistor M22 is turned on when a scan signal is suppliedto the ith scan line Si.

The twenty-third transistor M23 is coupled between the twenty-secondnode N22 and the anode electrode of the organic light emitting diodeOLED. In addition, a gate electrode of the twenty-third transistor M23is coupled to an (i−1)th light emitting control line Ei−1. Thetwenty-third transistor M23 is turned off when a light emitting controlsignal is supplied to the (i−1)th light emitting control line Ei−1, andturned on when the light emitting control signal is not supplied.

The twenty-fourth transistor M24 is coupled between the twenty-firstnode N21 and the first electrode of the twenty-first transistor M21. Inaddition, a gate electrode of the twenty-fourth transistor M24 iscoupled to the ith scan line Si. The twenty-fourth transistor M24 isturned on when the scan signal is supplied to the ith scan line Si.

The fifth stabilizing transistor MS5 is located on a current pathbetween the twenty-first node N21 and the first electrode of thetwenty-first transistor M21. For example, the fifth stabilizingtransistor MS5 may be located between the twenty-fourth transistor M24and the first electrode of the twenty-first transistor M21 or betweenthe twenty-first node N21 and the twenty-fourth transistor M24.

The fifth stabilizing transistor MS5 is formed as an oxide semiconductortransistor. Thus, if the fifth stabilizing transistor MS5 is turned off,leakage current between the twenty-first node N21 and the firstelectrode of the twenty-first transistor M21 is reduced or minimized.Accordingly, an image with a desired luminance can be implemented in thepixel PXL.

The twenty-fifth transistor M25 is coupled between a first power sourceVint′ and the anode electrode of the organic light emitting diode OLED.In addition, a gate electrode of the twenty-fifth transistor M25 isturned on when the scan signal is supplied to the ith scan line Si. Inaddition, a voltage of the first power source Vint′ is set such that theorganic light emitting diode OLED is turned off.

The twenty-sixth transistor M26 is coupled between the first drivingpower source ELVDD and the first electrode of the twenty-firsttransistor M21. In addition, a gate electrode of the twenty-sixthtransistor M26 is coupled to an ith light emitting control line Ei. Thetwenty-sixth transistor M26 is turned off when the light emittingcontrol signal is supplied to the ith light emitting control line Ei,and turned on when the light emitting control signal is not supplied.

The storage capacitor Cst is coupled between the twenty-first node N21and the twenty-second node N22 that is a common node between thetwenty-second transistor M22 and the twenty-third transistor M23. Thestorage capacitor Cst stores a voltage corresponding to the data signaland a threshold voltage of twenty-first transistor M21.

Meanwhile, in the pixel PXL of the present embodiment, the twenty-firstto twenty-sixth transistors M21 to M26 are N-type poly-siliconsemiconductor transistors. As described above, if the twenty-first totwenty-sixth transistors M21 to M26 are N-type poly-siliconsemiconductor transistors, fast driving characteristics can be ensured.

FIG. 16 illustrates another embodiment of a method for driving a pixel,for example, as shown in FIGS. 15A and 15B. Referring to FIG. 16, duringa first period T1′, the light emitting control signal is supplied to the(i−1)th light emitting control line Ei−1, and the scan signal issupplied to the ith scan line S1.

If the light emitting control signal is supplied to the (i−1)th lightemitting control line Ei−1, the twenty-third transistor M23 is turnedoff. If the twenty-third transistor M23 is turned off, the twenty-secondnode N22 and the anode electrode of the organic light emitting diodeOLED are electrically interrupted.

If the scan signal is supplied to the ith scan line Si, thetwenty-second transistor M22, the twenty-fourth transistor M24, and thetwenty-fifth transistor M25 are turned on. If the twenty-secondtransistor M22 is turned on, the data line Dm and the twenty-second nodeN22 are electrically coupled to each other. Then, the data signal fromthe data line Dm is supplied to the twenty-second node N22.

If the twenty-fourth transistor M24 is turned on, the twenty-first nodeN21 and the first electrode of the twenty-first transistor M21 areelectrically coupled to each other. At this time, the twenty-first nodeN21 is initialized to the voltage of the first driving power sourceELVDD. In addition, if the twenty-fourth transistor M24 is turned on,the twenty-first transistor M21 is diode-coupled.

If the twenty-fifth transistor M25 is turned on, the voltage of thefirst power source Vint′ is supplied to the anode electrode of theorganic light emitting diode OLED. Accordingly, the anode electrode ofthe organic light emitting diode OLED is initialized to the voltage ofthe first power source Vint′. At this time, the organic light emittingdiode OLED is set to the non-light emitting state.

During a second period T2′, the light emitting control signal issupplied to the ith light emitting control line Ei, and accordingly, thetwenty-sixth transistor M26 is turned off. If the twenty-sixthtransistor M26 is turned off, the first driving power source ELVDD andthe first electrode of the twenty-first transistor M21 are electricallyinterrupted.

At this time, since the second electrode of the twenty-first transistorM21 is set to the voltage of the first power source Vint′, thetwenty-first node N21 is set to a voltage obtained by adding a thresholdvoltage of the twenty-first transistor M21 to the voltage of the firstpower source Vint′. In addition, during the second period T2′, thetwenty-second node N22 is set to the voltage of the data signal. Thus,during the second period T2′, the storage capacitor Cst stores thevoltage corresponding to the data signal and the threshold voltage ofthe twenty-first transistor M21.

During a third period T3′, the supply of the light emitting controlsignal to the (i−1)th light emitting control line Ei−1 and the ith lightemitting control line Ei is stopped. If the supply of the light emittingcontrol signal to the (i−1)th light emitting control line Ei−1 isstopped, the twenty-third transistor M23 is turned on. If thetwenty-third transistor M23 is turned on, the twenty-second node N22 andthe anode electrode of the organic light emitting diode OLED areelectrically coupled to each other.

If the supply of the light emitting control signal to the ith lightemitting control line Ei is stopped, the twenty-sixth transistor M26 isturned on. If the twenty-sixth transistor M26 is turned on, the firstdriving power source ELVDD and the first electrode of the twenty-firsttransistor M21 are electrically coupled to each other.

At this time, the twenty-first transistor M21 controls the amount ofcurrent flowing from the first driving power source ELVDD to the seconddriving power source ELVSS via the organic light emitting diode OLED,corresponding to the voltage of the twenty-first node N21.

As described above, the pixel PXL of the present embodiment generateslight with a predetermined luminance while repeating the above-describedprocess during a period in which the organic light emitting displaydevice is driven at the first driving frequency. In addition, during theperiod in which the organic light emitting display device is driven atthe first driving frequency, the fifth stabilizing transistor MS5maintains the turn-on state, and accordingly, the pixel PXL can bestably driven.

Additionally, during a period in which the organic light emittingdisplay device is driven at the second driving frequency, the voltagecorresponding to the data signal is charged in the storage capacitor Cstof each of the pixels, and the control power source VC is then set tothe gate-off voltage. Then, the fifth stabilizing transistor MS5 in eachof the pixels PXL is turned off. Accordingly, the leakage currentbetween the twenty-first node N21 and the first electrode of thetwenty-first transistor M21 can be reduced or minimized. That is, thepixel PXL of the present embodiment can stably generate light with adesired luminance even when the organic light emitting display device isdriven at the second driving frequency.

FIGS. 17A and 17B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2005′ and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is coupledto the pixel circuit 2005′, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2005′.

The pixel circuit 2005′ controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS, via the organic light emitting diode OLED, corresponding to thedata signal.

The pixel circuit 2005′ includes a fifth stabilizing transistor MS5′located on a current path between the twenty-first node N21 and thefirst electrode of the twenty-first transistor M21. For example, thefifth stabilizing transistor MS5′ may be between the twenty-fourthtransistor M24 and the first electrode of the twenty-first transistorM21 or between the twenty-first node N21 and the twenty-fourthtransistor M24.

A gate electrode of the fifth stabilizing transistor MS5′ is coupled tothe ith scan line Si. The fifth stabilizing transistor MS5′ is turned onwhen the scan signal is supplied to the ith scan line Si, and turned offwhen the scan signal is not supplied. That is, the fifth stabilizingtransistor MS5′ is turned on or turned off simultaneously with thetwenty-fourth transistor M24.

An operating process of the pixel PXL will be described with referenceto FIGS. 16, 17A, and 17B. During the first period T1′, the lightemitting control signal is supplied to the (i−1)th light emittingcontrol line Ei−1, and the scan signal is supplied to the ith scan lineSi.

If the light emitting control signal is supplied to the (i−1)th lightemitting control line Ei−1, the twenty-third transistor M23 is turnedoff, and accordingly, the twenty-second node N22 and the anode electrodeof the organic light emitting diode OLED are electrically interrupted.

If the scan signal is supplied to the ith scan line Si, thetwenty-second transistor M22, the twenty-fourth transistor M24, thefifth stabilizing transistor MS5′, and the twenty-fifth transistor M25are turned on.

If the twenty-second transistor M22 is turned on, the data line Dm andthe twenty-second node N22 are electrically coupled to each other, andaccordingly, the data signal from the data line Dm is supplied to thetwenty-second node N22.

If the twenty-fifth transistor M25 is turned on, the voltage of thefirst power source Vint′ is supplied to the anode electrode of theorganic light emitting diode OLED, and accordingly, the anode electrodeof the organic light emitting diode OLED is initialized to the voltageof the first power source Vint′.

If the twenty-fourth transistor M24 and the fifth stabilizing transistorMS5′ are turned on, the twenty-first node N21 and the first electrode ofthe twenty-first transistor M21 are electrically coupled to each other.At this time, the twenty-first node N21 is initialized to the voltage ofthe first driving power source ELVDD.

During the second period T2′, the light emitting control signal issupplied to the ith light emitting control line Ei. Accordingly, thetwenty-sixth transistor M26 is turned off. If the twenty-sixthtransistor M26 is turned off, the first driving power source ELVDD andthe first electrode of twenty-first transistor M21 are electricallyinterrupted.

At this time, since the second electrode of the twenty-first transistorM21 is set to the voltage of the first power source Vint′, thetwenty-first node N21 is set to the voltage obtained by adding thethreshold voltage of the twenty-first transistor M21 to the voltage ofthe first power source Vint′. In addition, during the second period T2′,the twenty-second node N22 is set to the voltage of the data signal.Thus, during the second period T2′, the storage capacitor Cst stores thevoltage corresponding to the data signal and the threshold voltage ofthe twenty-first transistor M21.

During the third period T3′, the supply of the light emitting controlsignal to the (i−1)th light emitting control line Ei−1 and the ith lightemitting control line Ei is stopped. If the supply of the light emittingcontrol signal to the (i−1)th light emitting control line Ei−1 isstopped, the twenty-third transistor M23 is turned on. If thetwenty-third transistor M23 is turned on, the twenty-second node N22 andthe anode electrode of the organic light emitting diode OLED areelectrically coupled to each other.

If the supply of the light emitting control signal to the ith lightemitting control line Ei is stopped, the twenty-sixth transistor M26 isturned on. If the twenty-sixth transistor M26 is turned on, the firstdriving power source ELVDD and the first electrode of the twenty-firsttransistor M21 are electrically coupled to each other.

At this time, the twenty-first transistor M21 controls the amount ofcurrent flowing from the first driving power source ELVDD to the seconddriving power source ELVSS via the organic light emitting diode OLED,corresponding to the voltage of the twenty-first node N21.

Meanwhile, the fifth stabilizing transistor MS5′ maintains the turn-offstate during a period in which the pixel PXL emits light. If the fifthstabilizing transistor MS5′ is turned off, leakage current between thetwenty-first node N21 and the first electrode of the twenty-firsttransistor M21 is reduced or minimized during the period in which thepixel PXL emits light. Accordingly, light with a desired luminance canbe generated from the pixel PXL.

FIGS. 18A and 18B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2006 and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is coupledto the pixel circuit 2006, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2006.

The pixel circuit 2006 includes a sixth stabilizing transistor MS6located on a current path between the data line Dm and the twenty-secondnode N22. For example, the sixth stabilizing transistor MS6 may belocated between the twenty-second transistor M22 and the twenty-secondnode N22 or between the data line Dm and the twenty-second transistorM22.

A gate electrode of the sixth stabilizing transistor MS6 is coupled tothe control power source VC. The sixth stabilizing transistor MS6maintains the turn-on state when the organic light emitting displaydevice is driven at the first driving frequency. At this time, anoperating process of the pixel PXL is the same as described withreference to FIGS. 15A to 16.

Meanwhile, the sixth stabilizing transistor MS6 is turned off during aperiod in which the organic light emitting display device is driven atthe second driving frequency, i.e., a period in which the organic lightemitting display device is driven at a low frequency. The voltage of thecontrol power source VC is set to the gate-on voltage during a periodwhen the data signal is supplied to each of the pixels PXL. Accordingly,the voltage of the data signal is normally supplied to each of thepixels PXL.

After the data signal is supplied to each of the pixels PXL, the voltageof the control power source VC is set to the gate-off voltage.Accordingly, the sixth stabilizing transistor MS6 is turned off.

If the sixth stabilizing transistor MS6 is turned off, leakage currentbetween the data line Dm and the twenty-second node N22 is reduced orminimized. Accordingly, an image with a desired luminance can bedisplayed. In an embodiment of the present disclosure, the sixthstabilizing transistor MS6 is formed as an oxide semiconductortransistor, and accordingly, the leakage current can be reduced orminimized.

Meanwhile, in FIGS. 18A and 18B, it has been illustrated that the fifthstabilizing transistor MS5 is removed as compared with FIGS. 15A and15B, but the present disclosure is not limited thereto. For example, asshown in FIGS. 20A and 20B, the fifth stabilizing transistor MS5 and thesixth stabilizing transistor MS6 may be included in the pixel PXL.

FIGS. 19A and 19B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2006′ and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is coupledto the pixel circuit 2006′, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2006′.

The pixel circuit 2006′ controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS, via the organic light emitting diode OLED, corresponding to thedata signal.

The pixel circuit 2006′ includes a sixth stabilizing transistor MS6′ ona current path between the data line Dm and the twenty-second node N22.For example, the sixth stabilizing transistor MS6′ may be between thetwenty-second transistor M22 and the twenty-second node N22 or betweenthe data line Dm and twenty-second transistor M22.

A gate electrode of the sixth stabilizing transistor MS6′ is coupled tothe ith scan line Si. The sixth stabilizing transistor MS6′ is turned onwhen the scan signal is supplied to the ith scan line Si, and turned offwhen the scan signal is not supplied. An operating process of the pixelPXL is the same as described for FIGS. 16, 17A, and 17B.

If the sixth stabilizing transistor MS6′ is turned off, leakage currentbetween the data line Dm and the twenty-second node N22 is reduced orminimized. Accordingly, an image with a desired luminance can bedisplayed. In the present embodiment, the sixth stabilizing transistorMS6′ is formed as an oxide semiconductor transistor, and accordingly,the leakage current can be reduced or minimized.

Meanwhile, in FIGS. 19A and 19B, it has been illustrated the fifthstabilizing transistor MS5′ is removed as compared with FIGS. 17A and17B. In one embodiment, as shown in FIGS. 20C and 20D, the fifthstabilizing transistor MS5′ and the sixth stabilizing transistor MS6′may be in the pixel PXL.

FIGS. 21A and 21B illustrate additional embodiments of a pixel PXLlocated on an ith horizontal line and coupled to an mth data line Dm.Referring to FIGS. 21A and 21B, the pixel PXL includes an organic lightemitting diode OLED and a pixel circuit 2007 for controlling the amountof current supplied to the organic light emitting diode OLED. An anodeelectrode of the organic light emitting diode OLED is coupled to thepixel circuit 2007, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2007.

The pixel circuit 2007 controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS via the organic light emitting diode OLED, corresponding to a datasignal. To this end, the pixels circuit 2007 includes thirty-first tothirty-third transistors M31 to M33, a seventh stabilizing transistorMS7, a storage capacitor Cst, and a first capacitor C1.

A first electrode of the thirty-first transistor (or driving transistor)M31 is coupled to the first driving power source ELVDD, and a secondelectrode of the thirty-first transistor M31 is coupled to the anodeelectrode of the organic light emitting diode OLED. In addition, a gateelectrode of the thirty-first transistor M31 is coupled to athirty-first node N31. The thirty-first transistor M31 controls theamount of current flowing from the first driving power source ELVDD tothe second driving power source ELVSS via the organic light emittingdiode OLED, corresponding to a voltage of the thirty-first node N31.

The thirty-second transistor M32 is coupled between a first power sourceVint″ and the anode electrode of the organic light emitting diode OLED.In addition, a gate electrode of the thirty-second transistor M32 iscoupled to a second scan line S2. The thirty-second transistor M32 isturned on when a second scan signal is supplied to the second scan lineS2.

Here, the first power source Vint″ repeats a low voltage and a highvoltage during one frame period. The low voltage of the first powersource Vint″ is set to a voltage value such that the organic lightemitting diode OLED can be turned off. Also, the low voltage of thefirst power source Vint″ is set to a voltage higher than a low voltageof the first driving power source ELVDD. In addition, the second scanline S2 is commonly coupled to all of the pixels PXL. That is, in oneembodiment, the pixel PXL may be driven in a simultaneous light emittingscheme.

The thirty-third transistor M33 is coupled between the thirty-first nodeN31 and the second electrode of the thirty-first transistor M31. Agateelectrode of the thirty-third transistor M33 is coupled to an ith firstscan line S1 i. The thirty-third transistor M33 is turned on when afirst scan signal is supplied to the ith first scan line S1 i.

The seventh stabilizing transistor MS7 is located on a current pathbetween the thirty-first node N31 and the second electrode of thethirty-first transistor M31. For example, the seventh stabilizingtransistor MS7 may be between the thirty-third transistor M33 and thesecond electrode of the thirty-first transistor M31 or between thethirty-first node N31 and the thirty-third transistor M33.

A gate electrode of the seventh stabilizing transistor MS7 is coupled tothe control power source VC. The seventh stabilizing transistor MS7 isturned on or turned off corresponding to the voltage of the controlpower source VC.

The seventh stabilizing transistor MS7 is formed as an oxidesemiconductor transistor. Thus, if the seventh stabilizing transistorMS7 is turned off, leakage current between the thirty-first node N31 andthe second electrode of the thirty-first transistor M31 is reduced orminimized. Accordingly, an image with a desired luminance can beimplemented in the pixel PXL.

The storage capacitor Cst is coupled between the first power sourceVint″ and the thirty-first node N31. The storage capacitor Cst stores avoltage corresponding to the data signal and a threshold voltage of thethirty-first transistor M31.

The first capacitor C1 is coupled between the data line Dm and thesecond electrode of the thirty-first transistor M31. The first capacitorC1 controls a voltage of the second electrode of the thirty-firsttransistor M31 based on a voltage of data line Dm.

Meanwhile, in the pixel PXL of the present embodiment, the thirty-firstto thirty-third transistors M31 to M33 are N-type poly-siliconsemiconductor transistors. As described above, if the thirty-first tothirty-third transistors M31 to M33 are formed as poly-siliconsemiconductor transistors, fast driving characteristics can be ensured.

FIG. 22 illustrate another embodiment of a method for driving the pixelin FIGS. 21A and 21B. Referring to FIG. 22, during an eleventh periodT11, the first scan signal is supplied to the ith first scan line S1 i,and the second scan signal is supplied to the second scan line S2. Ifthe second scan signal is supplied to the second scan line S2, thethirty-second transistor M32 is turned on. If the thirty-secondtransistor M32 is turned on, a voltage of the first power source Vint″is supplied to the anode electrode of the organic light emitting diodeOLED. At this time, the organic light emitting diode OLED is set to thenon-light emitting state.

If the first scan signal is supplied to the ith first scan line S1 i,the thirty-third transistor M33 is turned on. If the thirty-thirdtransistor M33 is turned on, the thirty-first node N31 and the secondelectrode of the thirty-first transistor M31 are electrically coupled toeach other. At this time, the thirty-first node N31 is initialized tothe voltage of the first power source Vint″.

During a twelfth period T12, the first driving power source ELVDD dropsto a low voltage, and simultaneously, the supply of the second scansignal to the second scan line S2 is stopped. If the supply of thesecond scan signal to the second scan line S2 is stopped, thethirty-second transistor M32 is turned off.

If the first driving power source ELVDD drops to the low voltage,current is supplied from the anode electrode of the organic lightemitting diode OLED (i.e., the voltage of the first power source Vint″)to the first driving power source ELVDD by the diode-coupledthirty-first transistor M31. Thus, the thirty-first node N31 is finallyset to a voltage obtained by adding the threshold voltage of thethirty-first transistor M31 to the low voltage of the first drivingpower source ELVDD. That is, the threshold voltage of the thirty-firsttransistor M31 is compensated during the twelfth period T12. The storagecapacitor Cst stores a voltage of the thirty-first node N31 during thetwelfth period T12.

During a thirteenth period T13, the first driving power source ELVDD isset to a high voltage. In addition, the first scan signal issequentially supplied to the first scan lines S1 during the thirteenthperiod T13. If the first scan signal is supplied to the ith first scanline S1 i, the thirty-third transistor M33 is turned on. If thethirty-third transistor M33 is turned on, the voltage of thethirty-first node N31 is changed corresponding to a voltage of the datasignal supplied to the data line Dm. That is, the voltage of thethirty-first node N31 is changed corresponding to the voltage of thedata signal during the thirteenth period T13. In this case, the voltagecorresponding to the threshold voltage of the thirty-first transistorM31 and the data signal is stored in the storage capacitor Cst.

During a fourteenth period T14, the first power source Vint″ is set to ahigh voltage. If the first power source Vint″ is set to the highvoltage, the voltage of the thirty-first node N31 is increased bycoupling of the storage capacitor Cst. The thirty-first transistor M31controls the amount of current flowing from the first driving powersource ELVDD to the second driving power source ELVSS via the organiclight emitting diode OLED, corresponding to the voltage of thethirty-first node N31.

As described above, the pixel PXL of the present embodiment generateslight with a predetermined luminance while repeating the above-describedprocess during a period in which the organic light emitting displaydevice is driven at the first driving frequency. In addition, theseventh stabilizing transistor MS7 maintains the turn-on state duringthe period in which the organic light emitting display device is drivenat the first driving frequency. Accordingly, the pixel PXL can be stablydriven.

Additionally, during a period in which the organic light emittingdisplay device is driven at the second driving frequency, the voltagecorresponding to the data signal is charged in the storage capacitor Cstof each of the pixels PXL, and the control power source VC is then setto the gate-off voltage. Then, the seventh stabilizing transistor MS7included in each of the pixels PXL is turned off. Accordingly, theleakage current between the thirty-first node N31 and the secondelectrode of the thirty-first transistor M31 can be reduced orminimized. That is, the pixel PXL of the present embodiment can stablygenerate light with a desired luminance even when the organic lightemitting display device is driven at the second driving frequency.

FIGS. 23A and 23B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2007′ and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is coupledto the pixel circuit 2007′, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2007′.

The pixel circuit 2007′ controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS via the organic light emitting diode OLED, corresponding to thedata signal.

The pixel circuit 2007′ includes a seventh stabilizing transistor MS7′located on a current path between the thirty-first node N31 and thesecond electrode of the thirty-first transistor M31. For example, theseventh stabilizing transistor MS7′ may be located between thethirty-third transistor M33 and the second electrode of the thirty-firsttransistor M31 or between the thirty-first node N31 and the thirty-thirdtransistor M33.

A gate electrode of the seventh stabilizing transistor MS7′ is coupledto the ith first scan line S1 i. The seventh stabilizing transistor MS7′is turned on when the first scan signal is supplied to the ith firstscan line S1 i, and turned off when the first scan signal is notsupplied. That is, the seventh stabilizing transistor MS7′ is turned onor turned off simultaneously with the thirty-third transistor M33.

An operating process of the pixel PXL are described with reference toFIGS. 22, 23A, and 23B. First, during eleventh period T11, the firstscan signal is supplied to the ith first scan line S1 i, and the secondscan signal is supplied to the second scan line S2.

If the second scan signal is supplied to the second scan line S2, thethirty-second transistor M32 is turned on, and accordingly, the voltageof the first power source Vint″ is supplied to the anode electrode ofthe organic light emitting diode OLED.

If the first scan signal is supplied to the ith first scan line S1 i,the thirty-third transistor M33 and the seventh stabilizing transistorMS7′ are turned on. If the thirty-third transistor M33 and the seventhstabilizing transistor MS7′ are turned on, the thirty-first node N31 andthe second electrode of the thirty-first transistor M31 are electricallycoupled to each other. At this time, the thirty-first node N31 isinitialized to the voltage of the first power source Vint″.

During the twelfth period T12, the first driving power source ELVDDdrops to a low voltage, and simultaneously, the supply of the secondscan signal to the second scan line S2 is stopped. If the supply of thesecond scan signal to the second scan line S2 is stopped, thethirty-second transistor M32 is turned off.

If the first driving power source ELVDD drops to the low voltage,current is supplied from the anode electrode of the organic lightemitting diode OLED (i.e., the voltage of the first power source Vint″)to the first driving power source ELVDD by the diode-coupledthirty-first transistor M31. Thus, the thirty-first node 31 is finallyset to a voltage obtained by adding the threshold voltage of thethirty-first transistor M31 to the low voltage of the first drivingpower source ELVDD. The storage capacitor Cst stores the voltage of thethirty-first node N31 during the twelfth period T12.

During the thirteenth period T13, the first driving power source ELVDDis set to a high voltage. In addition, the first scan signal issequentially supplied to the first scan lines S1 during the thirteenthperiod T13. If the first scan signal is supplied to the ith first scanline S1 i, the thirty-third transistor M33 and the seventh stabilizingtransistor MS7′ are turned on.

If the thirty-third transistor M33 and the seventh stabilizingtransistor MS7′ are turned on, the voltage of the thirty-first node N31is changed corresponding to the voltage of the data signal supplied tothe data line Dm. That is, the voltage of the thirty-first node N31 ischanged corresponding to the voltage of the data signal during thethirteenth period T13. In this case, the voltage corresponding to thethreshold voltage of the thirty-first transistor M31 and the data signalis stored in the storage capacitor Cst.

During the fourteenth period T14, the first power source Vint″ is set toa high voltage. If the first power source Vint″ is set to the highvoltage, the voltage of the thirty-first node N31 is increased bycoupling of the storage capacitor Cst. At this time, the thirty-firsttransistor M31 controls the amount of current flowing from the firstdriving power source ELVDD to the second driving power source ELVSS, viathe organic light emitting diode OLED, based on the voltage of thethirty-first node N31.

Meanwhile, the seventh stabilizing transistor MS7′ maintains theturn-off state during a period in which the pixel PXL emits light. Ifthe seventh stabilizing transistor MS7′ is turned off, leakage currentbetween the thirty-first node N31 and the second electrode of thethirty-first transistor M31 is reduced or minimized during the period inwhich the pixel PXL emits light. Accordingly, light with a desiredluminance can be generated from the pixel PXL.

FIGS. 24A and 24B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2008 and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is coupledto the pixel circuit 2008, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2008.

The pixel circuit 2008 controls the amount of current flowing from thefirst driving power source ELVDD to the second driving power sourceELVSS, via the organic light emitting diode OLED, based on a datasignal.

The pixel circuit 2008 includes an eighth stabilizing transistor MS8 ona current path between the first power source Vint″ and the anodeelectrode of the organic light emitting diode OLED. For example, eighthstabilizing transistor MS8 may be between the first power source Vint″and the thirty-second transistor M32 or between the thirty-secondtransistor M32 and the anode electrode of the organic light emittingdiode OLED.

A gate electrode of the eighth stabilizing transistor MS8 is coupled tothe control power source VC. The eighth stabilizing transistor MS8maintains the turn-on state when the organic light emitting displaydevice is driven at the first driving frequency. At this time, anoperating process of the pixel PXL is the same as described withreference to FIGS. 21A to 22.

Meanwhile, the eighth stabilizing transistor MS8 is turned off during aperiod in which the organic light emitting display device is driven atthe second driving frequency, i.e., a period in which the organic lightemitting display device is driven at a low frequency. At this time, thevoltage of the control power source VC is set to the gate-on voltageduring a period in which the data signal is supplied to each of thepixels PXL. Thus, the voltage of the data signal is normally supplied toeach of the pixels PXL.

After the data signal is supplied to each of the pixels PXL, the voltageof the control power source VC is set to the gate-off voltage.Accordingly, the eighth stabilizing transistor MS8 is turned off. If theeighth stabilizing transistor MS8 is turned off, leakage current betweenthe first power source Vint″ and the anode electrode of the organiclight emitting diode OLED is reduced or minimized. Thus, an image with adesired luminance can be displayed. In the present embodiment, theeighth stabilizing transistor MS8 is an oxide semiconductor transistor.Thus, leakage current can be reduced or minimized.

Meanwhile, in FIGS. 24A and 24B, it has been illustrated that theseventh stabilizing transistor SM7 is removed as compared with FIGS. 21Aand 21B, but the present disclosure is not limited thereto. For example,as shown in FIGS. 26A and 26B, the seventh stabilizing transistor MS7and the eighth stabilizing transistor MS8 may be included in the pixelPXL.

FIGS. 25A and 25B illustrate additional embodiments of a pixel PXL whichincludes a pixel circuit 2008′ and an organic light emitting diode OLED.An anode electrode of the organic light emitting diode OLED is coupledto the pixel circuit 2008′, and a cathode electrode of the organic lightemitting diode OLED is coupled to the second driving power source ELVSS.The organic light emitting diode OLED generates light with apredetermined luminance corresponding to the amount of current suppliedfrom the pixel circuit 2008′.

The pixel circuit 2008′ includes an eighth stabilizing transistor MS8′on a current path between the first power source Vint″ and the anodeelectrode of the organic light emitting diode OLED. For example, theeighth stabilizing transistor MS8′ may be located between the firstpower source Vint″ and the thirty-second transistor M32 or between thethirty-second transistor M32 and the anode electrode of the organiclight emitting diode OLED.

A gate electrode of the eighth stabilizing transistor MS8′ is coupled tothe second scan line S2. The eighth stabilizing transistor MS8′ isturned on when the second scan signal is supplied to the second scanline S2, and turned off when the second scan signal is not supplied. Anoperating process of the pixel PXL may be the same as described withreference to FIGS. 22, 23A, and 23B.

If the eighth stabilizing transistor MS8′ is turned off, leakage currentbetween the first power source Vint″ and the anode electrode of theorganic light emitting diode OLED is reduced or minimized. Thus, animage with a desired luminance can be displayed. In the presentembodiment, the eighth stabilizing transistor MS8′ is an oxidesemiconductor transistor. Thus, leakage current can be reduced orminimized.

Meanwhile, in FIGS. 25A and 25B, it has been illustrated that theseventh stabilizing transistor MS7′ is removed as compared with FIGS.23A and 23B, but the present disclosure is not limited thereto. Forexample, as shown in FIGS. 26C and 26D, the seventh stabilizingtransistor MS7′ and the eighth stabilizing transistor MS8′ may beincluded in the pixel PXL.

The methods, processes, and/or operations described herein may beperformed by code or instructions to be executed by a computer,processor, controller, or other signal processing device. The computer,processor, controller, or other signal processing device may be thosedescribed herein or one in addition to the elements described herein.Because the algorithms that form the basis of the methods (or operationsof the computer, processor, controller, or other signal processingdevice) are described in detail, the code or instructions forimplementing the operations of the method embodiments may transform thecomputer, processor, controller, or other signal processing device intoa special-purpose processor for performing the methods described herein.

The drivers, controllers, processors, and other signal generating andsignal processing features of the disclosed embodiments may beimplemented in logic which, for example, may include hardware, software,or both. When implemented at least partially in hardware, the drivers,controllers, processors, and other signal generating and signalprocessing features may be, for example, any one of a variety ofintegrated circuits including but not limited to an application-specificintegrated circuit, a field-programmable gate array, a combination oflogic gates, a system-on-chip, a microprocessor, or another type ofprocessing or control circuit.

When implemented in at least partially in software, the drivers,controllers, processors, and other signal generating and signalprocessing features may include, for example, a memory or other storagedevice for storing code or instructions to be executed, for example, bya computer, processor, microprocessor, controller, or other signalprocessing device. The computer, processor, microprocessor, controller,or other signal processing device may be those described herein or onein addition to the elements described herein. Because the algorithmsthat form the basis of the methods (or operations of the computer,processor, microprocessor, controller, or other signal processingdevice) are described in detail, the code or instructions forimplementing the operations of the method embodiments may transform thecomputer, processor, controller, or other signal processing device intoa special-purpose processor for performing the methods described herein.

In accordance with one or more of the aforementioned embodiments, apixel and organic light emitting display device is provided where atleast one transistor on a leakage current path is an oxide semiconductortransistor. Accordingly, an image with a desired luminance can bedisplayed by reducing or minimizing leakage current.

In accordance with one or more of the aforementioned embodiments, atleast one transistor is provided on a leakage current path, where the atleast one transistor is turned off during at least a partial period inlow-frequency driving and is maintained in a turn-on state in othercases. Thus, leakage current can be reduced or minimized in thelow-frequency driving, and an image with a desired luminance can bedisplayed.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation. In someinstances, as would be apparent to one of ordinary skill in the art asof the filing of the present application, features, characteristics,and/or elements described in connection with a particular embodiment maybe used singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwiseindicated. Accordingly, various changes in form and details may be madewithout departing from the spirit and scope of the embodiments set forthin the claims.

What is claimed is:
 1. A pixel, comprising: an organic light emittingdiode; a first transistor to control an amount of current flowing from afirst driving power source to a second driving power source, via theorganic light emitting diode, based on a voltage of a first node; asecond transistor coupled between a data line and the first node, thesecond transistor to be turned on when a scan signal is supplied to ascan line; a storage capacitor coupled between the first node and asecond electrode of the first transistor; and a stabilizing transistorcoupled between the second transistor and the first node, wherein thefirst transistor and the second transistor are N-type poly-siliconsemiconductor transistors and the stabilizing transistor is an N-typeoxide semiconductor transistor.
 2. The pixel as claimed in claim 1,wherein: a gate electrode of the stabilizing transistor is coupled to acontrol power source, and the control power source is set to a gate-onvoltage during a period in which the pixel is driven at a first drivingfrequency and set to a gate-off voltage during a portion of a period inwhich the pixel is driven at a second driving frequency lower than thefirst driving frequency.
 3. The pixel as claimed in claim 2, wherein:when the pixel is driven at the second driving frequency, the controlpower source is set to the gate-off voltage after a voltage of a datasignal is stored in the storage capacitor.
 4. The pixel as claimed inclaim 1, wherein a gate electrode of the stabilizing transistor iscoupled to the scan line.
 5. The pixel as claimed in claim 1, furthercomprising: a third transistor coupled between the first driving powersource and a first electrode of the first transistor, the thirdtransistor having a turn-on period not overlapping a turn-on period ofthe second transistor.
 6. A pixel, comprising: an organic light emittingdiode; a first transistor to control an amount of current flowing from afirst driving power source to a second driving power source, via theorganic light emitting diode, based on a voltage of a first node; asecond transistor made of N-type poly-silicon semiconductor coupledbetween a data line and the first node, the second transistor to beturned on when a scan signal is supplied to a scan line; a stabilizingtransistor made of N-type oxide semiconductor coupled between the secondtransistor and the first node; and a storage capacitor coupled betweenthe first node and a second electrode of the first transistor.
 7. Thepixel as claimed in claim 6, wherein the first transistor is an N-typepoly-silicon semiconductor transistor.
 8. The pixel as claimed in claim7, wherein the first node is directly connected to a gate of the firsttransistor and a first electrode of the storage capacitor.
 9. The pixelas claimed in claim 7, wherein: a gate electrode of the stabilizingtransistor is coupled to a control power source, and the control powersource is set to a gate-on voltage during a period in which the pixel isdriven at a first driving frequency and set to a gate-off voltage duringa portion of a period in which the pixel is driven at a second drivingfrequency lower than the first driving frequency.
 10. The pixel asclaimed in claim 9, wherein: when the pixel is driven at the seconddriving frequency, the control power source is set to the gate-offvoltage after a voltage of a data signal is stored in the storagecapacitor.
 11. The pixel as claimed in claim 7, wherein a gate electrodeof the stabilizing transistor is coupled to the scan line.
 12. The pixelas claimed in claim 7, further comprising: a third transistor coupledbetween the first driving power source and a first electrode of thefirst transistor, the third transistor having a turn-on period notoverlapping a turn-on period of the second transistor.
 13. A pixel,comprising: an organic light emitting diode; a first transistor tocontrol an amount of current flowing from a first driving power sourceto a second driving power source, via the organic light emitting diode,based on a voltage of a first node; a second transistor coupled betweena data line and the first node, the second transistor to be turned onwhen a scan signal is supplied to a scan line; a storage capacitorcoupled between the first node and a second electrode of the firsttransistor; and a stabilizing transistor coupled between the data lineand the second transistor or between the second transistor and the firstnode, wherein: the second transistor is a poly-silicon semiconductortransistor and the stabilizing transistor is an oxide semiconductortransistor, a gate electrode of the stabilizing transistor is coupled toa control power source, and the control power source is set to maintaina gate-on voltage that is a constant voltage when the pixel is driven ata first driving frequency and set to a gate-off voltage during a portionof a period in which the pixel is driven at a second driving frequencylower than the first driving frequency.
 14. The pixel as claimed inclaim 13, wherein the first transistor and the second transistor areN-type poly-silicon semiconductor transistors and the stabilizingtransistor is an N-type oxide semiconductor transistor.
 15. The pixel asclaimed in claim 13, wherein: when the pixel is driven at the seconddriving frequency, the control power source is set to the gate-offvoltage after a voltage of a data signal is stored in the storagecapacitor.
 16. The pixel as claimed in claim 13, further comprising: athird transistor coupled between the first driving power source and afirst electrode of the first transistor, the third transistor having aturn-on period not overlapping a turn-on period of the secondtransistor.